1. Field of the Invention
This invention relates to an image formation apparatus such as a copying apparatus or a recording apparatus having a mechanism for manually or automatically feeding sheets.
2. Description of the Prior Art
There are known apparatus in which a sheet is fed from a place such as a cassette containing a number of sheets therein and exposure or image transfer is applied to the sheet to obtain a copy image or a sheet is manually fed to obtain a copy image thereon.
It is particularly convenient to manually feed a sheet along another path and preferentially obtain a copy image on the sheet which is different in size or paper quality from the sheets contained in the cassette.
However, provision of independent and exclusive paths for manually supply and automatic supply from a cassette which lead to the image formation station would result in a bulky and complicated construction of the copying apparatus.
Also, feeding sheets by the use of a common path would cause jam of the sheets or apparatus trouble which would be inconvenient to the operator.
In a case where the cassette process sequence is controlled by the same control circuit in accordance with various signals from the cassette, the process sequence concerned with the manual supply may also be controlled by those signals and this may cause a process trouble or cause formation of an incomplete image on the manually supplied sheet.
It would also be convenient to make it possible to form an image on manually supplied sheets of different sizes. However, when a sheet of a width smaller than the width of the insertion bed is inserted, the sheet may be obliquely inserted with a result that an image is formed at an unsuitable position on the sheet or the sheet jams.
In a case where a sheet is supported and fed so as to be inserted into the apparatus and then a copy start button is operated, the operator is required to use both of his hands and this means very poor operability. Moreover, it is very difficult to insert a sheet for straight feed and it is often the case that the sheet is fed obliquely.
Particularly, in a transfer type copying apparatus, where the sequence control is effected by detecting a manually supplied sheet, it is necessary to select the position of the sheet detector to an optimal position so as not to harm the image transfer registration. This imposes a limitation on the compactness of the copying apparatus.
In a transfer type copying apparatus, if the path leading to the image transfer station is long, sheet jam or image transfer misregistration is liable to occur. For example, there are apparatus in which a sheet is stopped by stopped register rollers and image transfer registration is effected by driving a roller in synchronism with the image on the drum. In this case, the sheet is caused to strike against the register rollers to provide a flexure of the sheet, but if the path to the register rollers is long, an appropriate flexure may not be provided sometimes. This may lead to poor registration accuracy or occurrence of sheet jam.
Also, in a transfer type copying apparatus, if the photosensitive drum is made small, the time required for the leading end of the image on the drum to reach the image transfer station from the start of copying becomes so much shorter that there is not enough time allowed for good image transfer registration to be obtained, and this may result in poor registration accuracy.
Further, in a transfer type copying apparatus, an image has been formed on the photosensitive drum by reciprocal movement of an original platen to make the apparatus compact and to obtain copies of a relatively large size. However, a complicated mechanism is necessary to move the platen and automatically return it and thus, low cost and compactness of the apparatus have been difficult to provide.
Also, the compactness of the copying apparatus has been limited due to the size of its photosensitive drum and the length of the optical path of the original image relative to the drum.